Polymer composition

ABSTRACT

Thermosetting moulding compositions comprising at least 50 percent of an inorganic filler, a high vinyl butadiene polymer, a free radical initiator and polyethylene in an amount less than 100 percent of the polymerisable material as shrink controller are described. The high vinyl butadiene polymer preferably contains 65 percent of 1,2-bonded units (i.e., units containing pendant vinyl groups) and can be used in conjunction with copolymerisable monomers. The polyethylene can be a homo- or copolymer and preferably has a density in the range 0.915 to 0.96. Low density or a mixture of low and high density polyethylene are particularly preferred. The compositions have low shrinkage on thermosetting and have good tensile strength in the thermoset state.

United States Patent 1191 Westermann et a1.

[ POLYMER COMPOSITION [73] Assignee: BP Chemicals International Limited,London, England [22] Filed: Oct. 25, 1972 [21] Appl. No.: 300,744

Related US. Application Data [63] Continuation-impart of Ser. No.164,419, July 20,

1971, abandoned.

[52] US. Cl 260/42.l8, 260/878 R, 260/889,

[51] Int. Cl C08d 9/08, C08f 29/04, C08f 29/08 [58] Field of Search260/878 R, 889, 41.5 R

[56] References Cited UNITED STATES PATENTS 2,832,748 4/1958 Safford eta1. 260/889 2,912,410 11/1959 Cole 260/889 3,741,931 6/1973 Martin eta1. 260/889 FOREIGN PATENTS OR-APPLICATIONS 589,941 12/1959 Canada260/889 June 28, 1974 842,205 7/1960 Great Britain 260/878 R PrimaryExaminer-Joseph L. Schofer Assistant Examiner-A. Holler [571 ABSTRACTThermosetting moulding compositions comprising at least 50 percent of aninorganic filler, a high vinyl butadiene polymer, a free radicalinitiator and polyethylene in an amount less than 100 percent of thepolymerisable material as shrink controller are described. The highvinyl butadiene polymer preferably contains 65 percent of 1,2-bondedunits (i.e., units containing pendant vinyl groups) and can be used inconjunction with copolymerisable monomers. The polyethylene can be ahomoor copolymer and preferably has a density in the range 0.915 to0.96. Low density or a,

mixture of low and high density polyethylene are particularly preferred.The compositions have low shrinkage on thermosetting and have goodtensile strength in the thermoset state.

12 Claims, No Drawings l POLYMER COMPOSITION This application is acontinuation-in-part of Ser. No. 164,419, filed July 20, 1971, nowabandoned.

The present invention relates to thennosetting moulding compositionsbased on high vinyl butadiene polymers and inorganic fillers.

Conventional polymers of 1,3-butadiene, for example those produced byfree radical aqueous emulsion processes, contain chains of polymerisedbutadiene units, each unit being chemically bonded to adjacent units inthe chain in either the l and 2 positions as shown in (a) or the l and 4positions as shown in (b).

Generally, free radical emulsion polymerisation tends to give butadienepolymer containing mainly the 1,4- bonded units and relatively few1,2-bonded units. Butadiene polymers and copolymers containing more thanabout 25 percent of the 1,2-bonded units are defined in thisspecification as high vinyl butadiene polymers and can be made, forexample, by alkali metal catalysed polymerisation. High vinyl butadienepolymers are known to have useful thermosetting properties.

By a thermosetting mouldingcomposition is meant throughout thisspecification a composition comprising at least 50 percent of aninorganic filler based on the weight of the total composition which canbe fabricated into hard infusible shaped articles by the action of heatand pressure, for example by pressing in a heated mould. Examples ofsuch thermosetting moulding compositions are reinforced or unreinforcedcompositions, preimpregnated mats or other forms of reinforcement inpreimpregnated form and preformed moulding compositions.

Examples of inorganic filler that can be used are various types ofcarbon blacks, silicas, aluminas, and calcium silicate, titaniumdioxide, zinc sulphide, calcium carbonate, zinc oxide, magnesia andclays. Part of the filler can consist of reinforcing materials such asfor example glass and asbestos fibres, woven or non-woven mats andchopped strands.

A problem encountered in the thermosetting of compositions of this typeis that of shrinkage, such shrinkage being particularly undesirable inmany moulding applications.

An object of the present invention is to provide thermosetting mouldingcompositions having improved properties. A further object of theinvention is to provide thermosetting moulding compositions havingreduced shrinkage properties.

Accordingly the present invention provides a thermosetting mouldingcomposition comprising (a) at least 50 percent by weight of an inorganicfiller (based on the weight of the total composition) and (b) apolymerisable component comprising a high vinyl butadiene polymer and afree radical initiator, in which the improvement consists of thepresence of a shrink controller, said shrink controller being anethylene homopolymer or an ethylene copolymer containing at least 85percent of copolymerised ethylene units, the

amount of said shrink controller being not more than 100 percent byweight of the amount of the polymerisable component.

Preferably the quantity of inorganic filler present is at least 200percent of the weight of the polymerisable component.

The high vinyl butadiene used in the composition of the presentinvention preferably contains at least 30 percent of 1,2-bonded unitsand most preferably at least 65 percent of 1,2-bonded units.Particularly useful thermosetting moulding compositions can be madeusing high vinyl butadiene polymer containing about 85 percent of1,2-bonded units. Suitably the viscosity average molecular weight of thepolymer is in the range 500 to 500,000 and preferably in the range 1000to 200,000, where the viscosity is measured in an Ostwald viscometerusing toluene as solvent at 25C and the viscosity average molecularweight is calculated from the intrinsic viscosity (1 using the equation(17) 1.69 X

The polymerisable component may contain a monomer or monomers known tocopolymerise with the high vinyl butadiene polymer for example styrene,vinyl toluene, diethyl fumarate, diethyl maleate, dibutyl fumarate,acrylamide, methacrylamide, N,N'-methylenebisacrylamide, ethylene glycoldimethacrylate, alkylmethacrylate and trimethylol propanetrimethacrylate.

Suitably the polymerisable component can contain up to 50 percent of thecopolymerisable monomer based on the weight of high vinyl butadienepolymer. A thermosetting moulding composition comprising a high vinylbutadiene polymer, a free radical initiator and an acrylamide compoundhaving the general formula H GCRCONHR wherein R is hydrogen or anorganic hydrocarbon substituent and R is hydrogen or an organicsubstituent is described in our British Patent Application No: 36295/filed July 27, 1970 referred to in the Application documents as CaseCPE.2894 and entitled Polymer Composition and in our corresponding US.Pat. application Ser. No: 164,421 filed July 20, 1971.

The initiator is suitably an organic peroxide compound examples of suchcompounds being ditertiarybutylperoxide, tertiarybutylperbenzoate,tertiarybutylperoctoate, benzoyl peroxide, 1,1-ditertiarybutylperoxy-3,3,S-trimethylcyclohexane andtertiarybutylperacetate. Useful thermosetting moulding compositions areobtained using bis( alkylperoxy) mon onuclear aromatic compounds asinitiators, for example, 1,3'or 1,4-bis (tertiarybutylperoxy isopropyi)benzene. A thermosetting moulding composition comprising a high vinylbutadiene polymer and a free radical initiator comprising a bis(alkylperoxy) mononuclear aromatic compound is described in our BritishPatent Application No: 36294/70 filed July 27, 1970 referred to in theApplication documents as Case CPE.2931 and entitled Polymer Compositionand in our corresponding US Pat. application Ser. No: 164,422 filed July20, 1971.

Mixtures of initiators can be used if desired.

Suitable concentrations of initiator used in the thermosetting mouldingcompositions are in the range 1 to 10 percent based on the weight ofhigh vinyl butadiene polymer.

- The polyethylene shrink controller used in the compositions of thepresent invention can be low, medium orhigh density polyethylene andmixtures of these can be used if desired. The preferred polyethyleneshrink controller has a density in the range 0.915 to 0.96. Low densitypolyethylene having a density in the range 0.915 to 0.925 isparticularly preferred.

In a preferred composition according to the present invention thepolyethylene shrink controller comprises a mixture of low densitypolyethylene having a density in the range 0.915 to 0.925 with a highdensity polyethylene having a density above 0.94. When it is desired touse a blend of this type the ratio of low density to high densitypolyethylene in the blend is preferably in the range 3:1 to 1:3. Thedensities of the polyethylene throughout this specification are given ing/ml and are measured by the method described in British StandardSpecification 2782, Method 509A.

Preferably the concentration of the polyethylene shrink controller is atleast 5 percent based on the weight of the polymerisable component andmost preferably is in the range to 70 percent.

In a preferred composition according to the present invention thepolymerisable component consists only of high vinyl polybutadiene and afree radical initiator.

If desired, additional materials capable of controlling shrinkage can beincorporated in the thermosetting moulding compositions of the presentinvention for example polystyrene, poly-N-phenylacrylamide andchlorinated polyethylene; polymeric materials such as rubbery or liquidisobutene polymers; and saturated liquid polymers such as polypropyleneadipate, polypropylene sebacate and polypropylene glycol.

When it is desired to incorporate polystyrene into the composition ofthe present invention, preferably monomeric styrene is also incorporatedat a concentration in the range 100 to 200 percent based on the weightof the polystyrene.

The various components of the thermosetting moulding compositions of thepresent invention can be mixed together in any order, conventionalmixing apparatus being used if desired. If desired, a diluent forexample hexane or toluene can be used to facilitate the mixing of thecomponents and all, or the bulk of the diluent can then be removed undervacuum or by heating to a temperature below about 100C preferably undervacuum or in a stream of nitrogen. Heating the composition totemperatures not greater than about 100C can also be used to promotebetter mixing of the components.

When glass fibre is used as reinforcement in the compositions of thepresent invention it is preferred to use at least some diluent tofacilitate the mixing and minimise mechanical damage to the fibre.

Where fillers such as glass fibre, silica, quartz or clay areincorporated in the thermosetting moulding compositions of the presentinvention, adhesion promoting silanes for example vinyltris(beta-methoxy ethoxy) silane can, if desired, be included to improve theadhesion between the filler and the thermoset components in thethermoset products.

Antioxidants for example butylated hydroxy toluene (BHT) can beincorporated in the thermosetting moulding compositions of the presentinvention to prolong their shelf life.

The thermosetting of the moulding compositions is suitably carried outat temperatures in the range l40 to 250C and at pressure in excess of100 psig.

EXAMPLE 1 A thermosetting moulding composition was prepared using thefollowing ingredients:

High vinyl butadiene polymer M 25,000 85 pbw l,2 content 76% Calciumcarbonate filler 300 1,3 bis (t-butylperoxyisopropyl) benzene 4 Lowdensity polyethylene (sold under the trade name of Alkathene 200 by ICI)40 V4 inch chopped glass fibres Mixing was continued for 10 minutes at100C by which time the low density polyethylene was well dispersed inthe thermosetting moulding composition.

Test specimens of this composition were moulded at 180C for 5 minutes atapproximately 10 tons/sq. in. The physical properties of the testspecimens were as follows:

Flexural modulus Kg/cm 60,000 Flexural strength Kg/cm l,l60 Tensilestrength Kg/cm 350 Impact strength Kg/cm'lcm l8 Mould shrinkage cm/cm0.0026 Barcol hardness 27 The mouldings containing polyethylene showed asmooth surface free of cracks and ripple and 1 mm thick mouldings didnot warp.

EXAMPLE 2 A thermosetting moulding composition was prepared from thefollowing ingredients:

High vinyl butadiene polymer (M'\T= l2,000

l,2 content 72%) pbw Calcium carbonate filler 300 I3 bis (t-butylperoxyisopropyl) benzene 4 Low density polyethylene (sold under the trade nameof Alkathene 200) 20 High density polyethylene (sold under the tradename of Rigidex T) l0 inch chopped gl'ass fibres .75

Mixing was carried out for 15 minutes at C by which time both the lowdensity and high density polyethylenes were well dispersed in thethermosetting moulding composition.

Test specimens of this composition were moulded at C for 5 minutes andthe following results were obtained.

Flexural modulus Kg/cm 62.000 Flexural strength Kg/cm l,0l0 Tensilestrength Kg/cm 390 Impact strength Kg/cm/cm 24 Mould shrinkage cm/cm0.0025 Barcol hardness 46 Muldihg5 made from this composition wereSimilar 3. A thermosetting moulding composition according to thoseobtained in Example 1. in addition impact to claim 1 wherein the amountof filler present is at strength and Barcol hardness were improved bythe use least 200 percent of the weight of the polymerisable of amixture of high and low density polyethylene p n n rather than lowdensity polyethylene on its own.

thehhesettthg moulding eempeshioh according to claim 1 wherein thepolymensable component con- EXAMPLES 3 6 tains a tlmolnorlner ormrlmomers capable of copolymerising wi t e i vin butadiene l mer. i p ti g z g g to 5. thermose tting moulding co i p osition according e Xampes an an y way to claim 4 wherein the copolymerisable monomer oreompahseh (Examples 3 and 4) e P p by monomers are selected fromstyrene, vinyl toluene, dimlxlhg the components Table m a Brabehderethyl fumarate, diethyl maleate, dibutyl fumarate, ac- Plastograph usmga rubber mixing head. All four comrylamide, methyacrylamide, N,N-positions each contained calcium carbonate filler (300methylenebisacrylarnide, ethylene glycol dimethacryp.b.w.), /iinchchopped glass fibre(75 p.b.w.)and 1,3- late, allyl methacrylate andtrimethylol propane tribis-(t-butylperoxyisopropyl) benzene (4 p.b.w.)in admethacrylatei dition to the components shown in the Table l. The

thetmosettlhg moulding e 'lpee eeeetdthg mixing was carried out at atemperature of 120C to claim 1 wherein the free radical initiator 1Sdlcumyl for 10 minutes. The moulding compositions were i g mouldingcomposition according O I i o n u a I I then thermoset at 180 C for 5mmutes m amould at '2 to claim 1 wherein the free radical initiator is1,3 or

proximately 10 tons per square inch. The mould shrmkl4 bis (tefliarybmylperoxy isopropyl) benzene age on thefmosewqg for each composmohwas meat8. A thermosetting mouldingcomposition according Shred and 15 ShownTable I g g to claim 1 wherein the polyethylene shrink controller TABLE1 i High Vinyl Polyethylene Weight ratio of Mould Example ButadieneAlkathene 200" Polyethylene: Shrinkage No. Polymer (p.b.w.) High vinylcm/cm (p.b.w.) butadiene polymer Notes on Table 1.

p.b.w. =parts by weight I The high vinyl butadiene had Mv= 6046 andcontained 83% of 1,2-polymerised units. Alkathene 200 is a low densitypolyethylene commercially available from Imperial Chemical IndustriesLtd.

Example 3 demonstrates the mould shrinkage of a 40 i l w d ity ly th l nh i a d i i h high vinyl butadiene polymer thermosetting moulding range0.915 to 0.925. composition comprising no polyethylene shrink con- 9.thermosetting moulding composition according troller. Example 4demonstrates that when the polyet0 elalml wherein the p lyethylen ShrinkController thylenezhigh vinyl butadiene polymer ratio is 60:40 the is amixture of tow and high density Polyethylene, the

mould shrinkage is greater than when no polyethylene densityPolyethylene minimum density of is present in the composition. When theratio is :50 A th ermosettlng moulding composition accordwhen the amountof polyethylene 94 percent by ing to claim 1 wherein the concentrationof the poly- Wetght of the amount of the polymerisable component)ethylene shrink controller is in the range 10 to 70 per-- it can be seenthat shrinkage control is obtained (cf Excent based on the weight of thepolymerisable Compo amples 3 and 5). Example 6 demonstrates that even 50Hem.

better shrinkage control occurs when the ratio is 32:68. 11, A th ttildi composition f duced shrinkage properties as compared to a like comwl i position free from a shrinkage control agent, which 1. in athermosetting moulding composition compris eemposttloh Comprises atleast 50 Peteeht to at least ing (a) at least 50 percent by weight of aninorganic 200 Percent y Weight of an inorganic fihel', based on filler,based on the weight of the total composition, and the g t the p ym l ompn Which at- (b) apolymerisable component comprisinga high vinyl p p s ahigh butadlehe y 3 free butadiene polymer and a free radical initiator,the imh h g t gi 5 Percent t e n t provement consistmg m the presence ofat least 5 per- 5 "g whicfii sgg tlfi leg iorglqtgonein o as 2131 centbased on the weight of the polymerisable compo- 0 l Y e 1%; ymet nent ofa shrink controller, said shrug: controller being 2 gQP :2% i o thm t gsaf an ethylene homopolymer or are ylene copolymer 0 e h h e orcontaining at least percent of copolymerized ethylpercent by Weight ofthe amount of the Polythene?! ene units, the amount of said shrinkcontroller being i h lii ig g moulding composition accord iii: gsg n r iahe ihiai iiezi of the amount of 65 ing to claim 11 wherein the shrinkcontroller is a mix- 2. thermosetting mouldingcomposition according g ggg yg r a e e y mdthe gb of to claim 1 wherein the high vinyl butadienepolymer 1 t0 ah Peyet Y ehe avlhg a ehslty a (We contains at least 65percent of 1,2-bonded units. 094 in the ratio of 3 i

2. A thermosetting moulding composition according to claim 1 wherein thehigh vinyl butadiene polymer contains at least 65 percent of 1,2-bondedunits.
 3. A thermosetting moulding composition according to claim 1wherein the amount of filler present is at least 200 percent of theweight of the polymerisable component.
 4. A thermosetting mouldingcomposition according to claim 1 wherein the polymerisable componentcontains a monomer or monomers capable of copolymerising with the highvinyl butadiene polymer.
 5. A thermosetting moulding compositionaccording to claim 4 wherein the copolymerisable monomer or monomers areselected from styrene, vinyl toluene, diethyl fumarate, diethyl maleate,dibutyl fumarate, acrylamide, methyacrylamide,N,N''-methylenebisacrylamide, ethylene glycol dimethacrylate, allylmethacrylate and trimethylol propane trimethacrylate.
 6. A thermosettingmoulding composition according to claim 1 wherein the free radicalinitiator is dicumyl peroxide.
 7. A thermosetting moulding compositionaccording to claim 1 wherein the free radical initiator is 1,3 or1,4-bis-(tertiarybutyl peroxy isopropyl) benzene.
 8. A thermosettingmoulding composition according to claim 1 wherein the polyethyleneshrink controller is low density polyethylene having a density in therange 0.915 to 0.925.
 9. A thermosetting moulding composition accordingto claim 1 wherein the polyethylene shrink controller is a mixture oflow and high density polyethylene, the high density polyethylene havinga minimum density of 0.94.
 10. A thermosetting moulding compositionaccording to claim 1 wherein the concentration of the polyethyleneshrink controller is in the range 10 to 70 percent based on the weightof the polymerisable component.
 11. A thermosetting moulding compositionof reduced shrinkage properties as compared to a like composition freefrom a shrinkage control agent, which composition comprises at least 50percent to at least 200 percent by weight of an inorganic filler, basedon the weight of the polymerisable component, which latter comprises ahigh vinyl butadiene polymer, a free radical initiator and at least 5percent based on the weight of the polymerisable component of a shrinkcontroller which is an ethylene homopolymer or an ethylene copolymercontaining at least 85 percent of copolymerized ethylene units in anamount not more than 100 percent by weigHt of the amount of thepolymerisable component.
 12. A thermosetting moulding compositionaccording to claim 11 wherein the shrink controller is a mixture ofpolyethylene having a density in the range of 0.915 to 0.96 andpolyethylene having a density above 0.94 in the ratio of 3:1 to 1:3.